package twopoint;
 class ListNode {
      int val;
      ListNode next;
      ListNode() {}
      ListNode(int val) { this.val = val; }
      ListNode(int val, ListNode next) { this.val = val; this.next = next; }
  }

class 链表的中间节点_876 {
            public ListNode middleNode(ListNode head) {
                ListNode fast = head, slow = head;
                while(fast!= null && fast.next != null) {
                    fast = fast.next.next;
                    slow = slow.next;
                }
                return slow;
            }
        }
